Presently, single current or voltage sensing devices exist. In case of sensing voltage and/or current on a disconnecting or switching device, two voltage measurements are installed at both ends of a switching device in order to cover both, connected and disconnected states of the device. It is sufficient to sense current only at one end of the device as the current is flowing only in the case of a connected state of the switching device.
A known approach of sensing current and voltage over switching devices uses one separate current sensing device and two separate phase-to-ground voltage sensing devices located each on different sides of the swithing device.
WO 2008/151937 as well as EP 0 510 311 A2 disclose voltage and/or current sensor devices, which are integrated in the same isolation body as the high-voltage switch itself. So capacitive and/or inductive disturbances as well as the inability of changing or retrofitting the sensor devices, can be disadvantages of these known state of the art constructions.